81731 has 4 divisors (see below), whose sum is σ = 88032. Its totient is φ = 75432.

The previous prime is 81727. The next prime is 81737. The reversal of 81731 is 13718.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81731 - 2² = 81727 is a prime.

It is a super-2 number, since 2×81731² = 13359912722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81737) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3131 + ... + 3156.

It is an arithmetic number, because the mean of its divisors is an integer number (22008).

2⁸¹⁷³¹ is an apocalyptic number.

81731 is a deficient number, since it is larger than the sum of its proper divisors (6301).

81731 is a wasteful number, since it uses less digits than its factorization.

81731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6300.

The product of its digits is 168, while the sum is 20.

The square root of 81731 is about 285.8863410518. The cubic root of 81731 is about 43.3972560859.

It can be divided in two parts, 817 and 31, that added together give a palindrome (848).

The spelling of 81731 in words is "eighty-one thousand, seven hundred thirty-one".